Single Actuator Configuration for a Camera Module

ABSTRACT

Systems and methods for camera modules having a movable lens barrel, allowing a maximum lens diameter with minimal outside dimensions are disclosed. At least one single linear actuator is moving the lens barrel. Each actuator is deployed in an own corner of the camera module. The moving lens barrel is guided by rolling elements bearings. The actuator comprises a stator, comprising one or more coils wrapped around a rod of magnetic metal and an anchor comprising one or more permanent magnets, which are tightly attached to the lens barrel. An offset between the longitudinal center line of magnets of the anchor and the center of the stator generates a permanent force pushing the lens barrel in direction of the stator of the motor and consequently pushes protrusions on the lens barrel onto the rolling elements bearings, thus preventing the bearings to fall apart in case of a mechanical shock.

This is a continuation of U.S. patent application Ser. No. 12/806,322,filed on Aug. 10, 201002, which is herein incorporated by reference inits entirety, and assigned to a common assignee.

RELATED APPLICATIONS

This application is related to the following US patent applications:

-   DI09-003/004, titled “Camera module having a low-friction movable    lens”, Ser. No. 12/661,752, filing date Mar. 23, 2010,-   DI09-007, titled “Twin-actuator configuration for a camera module”,    Ser. No. 12/661,755, filing date Mar. 23, 2010, and-   DI09-017, titled “Linear motor with integrated position sensor”,    Ser. No. 12/799,947, filing date May 5, 2010,-   which are assigned to the same assignee. The contents of these    applications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to camera modules and relates morespecifically to camera modules having a movable lens barrel and whereinthe actuators are deployed in a way to achieve minimal size of thecamera module.

2. Description of the Prior Art

Digital camera modules are used with many electronic devices such ase.g. mobile phones, personal data assistants (PDAs), computers, etc.These camera modules have to be as small as possible, reliable, and easyto be used, robust and require minimal power consumption. Furthermorethe design of the camera modules should allow low manufacturing cost,while the quality of the images has to conform to a high standard.

Therefore modern camera modules should allow auto-focusing and minimalfriction of the bearing for a movable lens barrel in order to achieveprecise focusing of the camera.

It is important that the camera modules, which are to be built in mobileelectronic devices as e.g. mobile phones, require minimal size. It is achallenge for the designers of camera modules to develop auto-focuscamera modules having a reliable drive for moving a lens barrel havingminimal size and consuming minimal power.

Solutions dealing with the design of cameras and related auto-focusdrives are described in following patents:

U.S. Patent (U.S. Pat. No. 7,400,068 to Tseng) teaches a voice coilmotor apparatus applied to an auto-focus or variable-focus lens moduleof a miniaturized camera including: a voice coil motor, a plurality ofsteel guidance shafts, a lens holder, and a base. The voice coil motoralso includes a magnetic part including magnets and yokes, and anelectrical part including a coil winding. The magnetic part is rigidlycoupled to the lens holder to form the moving member. The electricalpart and the steel guidance shafts are fixed on the base to form thenon-moving member. The pre-loaded force due to the interaction betweenthe leakage flux of the magnetic part and the steel guidance shaftseliminates the free-play resulting from the tolerance gap between themoving and the non-moving members, and that the magnets and the yokesform a non-circular magnetic structure having a rectangular contour inorder to minimize the overall dimension.

U.S. Patent (U.S. Pat. No. 4,873,542 to Nakayama) discloses anauto-focus camera having a focusing lens supporting feed screw rodsupported substantially parallel to the lens optical axis and having aslit for focusing at its one end, and a spacer nut meshed with a feedscrew portion of the feed screw rod, so that is longitudinal movement isprevented, and rotated by the focus control motor.

U.S. Patent (U.S. Pat. No. 4,783,676 to Aihara et al.) discloses a lensdrive device for a camera driving a lens by a motor to a position presetby an operator. The lens position is stored in a memory. When the lensis to be moved to the stored position while the lens is moved by anauto-focus device to an in-focus position, the lens is instantly movedby the motor to the stored position based on the data stored in thememory.

SUMMARY OF THE INVENTION

A principal object of the present invention is to achieve methods andsystems to achieve camera modules having a movable lens barrel, allowinga maximum lens diameter with minimal outside dimensions

A further object of the present invention is to use only one actuator tomove the lens barrel.

A further object of the present invention is to deploy the actuator in aseparate corner of the camera module.

A further object of the present invention is to use rolling bearings toguide the movements of the lens barrel.

A further object of the present invention is to secure a safe operationof the rolling-elements bearings in case of a mechanic shock.

In accordance with the objects of this invention a method for cameramodules having a movable lens barrel allowing a maximum lens diameterwith minimal outside dimensions has been achieved. The method inventedcomprises the following steps of: (1) providing a camera modulecomprising a movable lens barrel driven by at least one single linearactuator, (2) deploying the actuator in a corner of the camera module,(3) guiding the movements of the lens barrel driven by said at least oneactuator to a desired position by rolling elements bearings, and (4)applying a pre-load force to the rolling elements bearings, wherein thisforce is present in any position of the lens barrel.

In accordance with the objects of this invention a camera module havinga movable lens barrel, allowing a maximum lens diameter with minimaloutside dimensions has been achieved. The camera module inventedcomprises: an image sensor, a shutter with an aperture function drivenby a linear motor, said motor driving the shutter, wherein the motor hasan integrated position sensing system, and a movable lens barrel.Furthermore the camera module invented comprises at least one linearactuator to move said lens barrel, wherein each actuator is deployed inan own corner of the camera module, wherein the actuators are generatinga pre-load force on rolling elements bearings, an integrated circuitcontrolling the motor driving the shutter and the actuators moving thelens barrel, and said rolling elements bearings wherein the rollingelements of each bearing are moving between the lens barrel and a fixedpart of the camera.

In accordance with the objects of this invention a camera module havinga movable lens barrel, allowing a maximum lens diameter with minimaloutside dimensions has been achieved. The camera module inventedcomprises: a movable lens barrel, at least one single linear actuator tomove said lens barrel, wherein each actuator comprises a stator,fastened on a frame of the camera module, and an anchor, fastened on thelens barrel, and wherein each actuator is deployed in an own corner ofthe camera module, and a means to guide the movements of the lensbarrel.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings forming a material part of thisdescription, there is shown:

FIG. 1 shows an oblique view a camera module of the present invention.

FIG. 2 shows a top view on the camera module invented illustrating thelens and actuator integration.

FIG. 3 a illustrates the magnetic retention system of the presentinvention.

FIG. 3 b shows in detail a top view of the actuator of the presentinvention including the coil assembly of the stator and the magnetassembly of the moving anchor.

FIG. 4 illustrates an arrangement of a lens barrel, ball bearings and anactuator.

FIG. 5 illustrates a top view of the camera module invented inclusiveball cages of ball bearings.

FIG. 6 shows a side view of an arrangement of balls, a ball cage, and acorrespondent bearing pin.

FIG. 7 illustrates a flowchart of a method invented for camera modulescomprising a movable lens barrel, allowing a maximum lens diameter withminimal outside dimensions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments disclose methods and systems to design cameramodules having a movable lens barrel driven, by a single linear actuatorand allowing a maximum lens diameter with minimal outside dimensions.

Preferred embodiments of the invention are characterized by using onlyone linear actuator to move a lens barrel. This single actuator islocated in one corner of a camera module. It should be understood thatalternatively more than one actuator could be used to drive the lensbarrel. Using actuators with more than one anchor would be possible aswell.

In preferred embodiments of the invention an actuator with integratedposition detection is used to drive the movable lens barrel and tocontrol an actual position of the lens barrel, e.g. as disclosed in thepatent application DI09-017, titled “Linear motor with integratedposition sensor”, Ser. No. 12/799,947, filing date May 5, 2010. Otherposition sensing methods as e.g. capacitive sensors or Hall sensorscould be used as well.

All embodiments of the present invention achieve minimal outerdimensions by using one actuator only to move the lens barrel and havethis actuator deployed in a corner of the camera module. The actuatorscan be built smaller if more than one actuator is used.

In a first preferred embodiment, the invention has been used with acamera module using ball bearings as shown in FIG. 1.

FIG. 1 shows an oblique view of an embodiment of the camera moduleinvented. It shows a single actuator unit 1 comprising a flexibleprinted circuit (FPC), a stator 5, having two coils 2 wrapped aroundmagnetic metal as e.g. iron, and an anchor, comprising two magnetsfastened on it. Alternatively only one coil or more than two coils couldbe used with the stator and also only one magnet or more than twomagnets could be deployed on the anchor. The anchor is firmly attachedto the lens barrel. The actuator is driving the lens barrel 3 to aposition desired along the optical axis of the camera dependent uponcurrents in the two coils. The actuator may have an integrated positionsensing capability or other methods to sense the position of the movinglens barrel can be applied, i.e. using for example capacitive sensors,Hall sensor or magnetic sensors.

Furthermore the camera comprises a module carrier 4, comprising anintegrated circuit (IC) to control the operation of the camera and animage sensor.

In a preferred embodiment of the invention a bidirectional actuator,comprising the stator having coils wrapped around magnetic metal,preferably iron, and the moving anchor having at least at least onepermanent magnet, is deployed to move the lens barrel shown in of FIGS.1-2. The actuator is used to move the lens barrel and the permanentmagnet is mounted on the lens barrel and the iron carrying the coils ismounted on the carrier.

Furthermore FIG. 1 shows a movable lens barrel 3, which is moved by theactuator unit 1 and guided by e.g. rolling elements bearings (not shownin FIG. 1) to achieve minimal friction of the movement of the lensbarrel. The actuator fits into one of the corners of the camera modulewith minimum extra space requirement because the lens and lens barrelare round and the camera module is rectangular.

FIG. 2 shows a top view on the camera module invented illustrating thelens and actuator integration. It shows the coil assembly 2 of thestator, the magnet assembly 20 of the moving anchor, which is firmlyattached to the lens barrel 3, and the ball bearings 21. Alternativelyany rolling elements bearings, as e.g. roller bearings could be used aswell instead of ball bearings. Furthermore a nose 22 is deployed on thelens barrel for one or more rolling elements bearing, wherein the ballsare moving between a corresponding nose 22 and a fixed frame 23. Placingthe actuator and rolling elements bearings 21 in corners of the cameramodule as shown in FIG. 2 allows a maximum diameter of the lens barrel 3in a given package size.

FIG. 3 a illustrates the magnetic retention system of the presentinvention. In order to minimize the the force required for lensdisplacement, mechanical sources of friction need to be eliminated asfar as possible. The magnetic retention system has no friction sourcesexcept the rolling elements bearings.

As shown in detail in FIG. 3 b there is an offset between thelongitudinal center line of the magnets of the anchor and thelongitudinal center line of the stator, i.e. the midline of the coils.This offset generates a permanent force in the direction of the arrow ofFIG. 3 a, i.e. independently of the actual position of the lens barrel,which is moving along the optical axis, this force pushes the lensbarrel in the direction of the stator of the motor and consequentlypushes the nose 30 of the lens barrel onto the correspondent rollingelements bearing, thus preventing the rolling element bearing to fallapart in case of a mechanical shock. In a preferred embodiment of theinvention ball bearings 31 and 32 are used for rolling elements bearingsand furthermore the part of the nose 30 pushing on the rolling element,e.g. ball 31, has about a same orientation as a midline of the linearactuator. In the preferred embodiment of FIG. 3 a a nose in form of a aprotrusion 32 is deployed in order to provide a area to put pressure onthe ball 32, wherein this pressure is provided by the bearings pre-loadof the actuator. Each rolling element of the bearings is moving betweena correspondent nose or protrusion 30/32 of the moving lens barrel, thefixed frame 21 of the camera module, and also potentially a part of thelens barrel being close to the corresponding nose/protrusion.

It should be noted that FIG. 3 a illustrates anon-limiting example ofthe camera module invented. Other kinds of rolling elements bearings,other numbers of rolling elements bearings, and other geometries of thenoses/protrusions could alternatively be used with the presentinvention.

FIG. 3 b shows the area surrounded by dotted lines of FIG. 3 a enlarged.It shows in detail a top view of the actuator of the present inventionincluding the coil assembly 2 of the stator and the magnet assembly 20of the moving anchor. The one or more permanent magnets of the magnetassembly 20 generate an attraction force to the metal coil core of thestator 2.

The arrows 34 illustrate the direction of magnetic force used for thepre-load of the bearings indendent of the actual position of the lensbarrel, which can be moved to a position desired along the optical axisof the camera module.

FIG. 4 illustrates a preferred embodiment of an arrangement of a lensbarrel, ball bearings and an actuator comprising a stator 5 and ananchor 20 according to the invention. The same numerals for likecomponents are used with FIG. 4 as with FIGS. 1-3 a+b. FIG. 4 depicts alens barrel 3, wherein the anchor 20 with one or more permanent magnetsis fixedly fastened on the lens barrel 20. The stator comprises twocoils 2 wrapped around a piece of magnetic metal. On the left side ofthe lens barrel are two balls 31 and an arrangement of correspondentnoses 30. On the opposite side of the lens barrels are two balls 32 anda correspondent protrusion 33.

FIG. 5 illustrates a top view of the camera module invented inclusiveball cages of ball bearings. FIG. 5 shows again the lens barrel 3, astator 5 of the actuator and a correspondent anchor 20, a ball 31 with acorrespondent nose 30, and on the opposite side a ball 32 with acorrespondent protrusion 33. Furthermore it shows ball cages 50 aroundboth balls 31 and 32 and a bearing pin 51 for each ball bearing. Thisbearing pin 51 is used to avoid creeping of the lens barrel by keepingballs and cages in place in case of any mechanical shock. Such a bearingpin has been disclosed in the patent application DI09-003/004, titled“camera module having a low-friction movable lens”, Ser. No. 12/661,752,filing date Mar. 23, 2010.

FIG. 6 shows a side view of an arrangement of balls, a ball cage 50, anda correspondent bearing pin 51. The ball cage 51 is used to keep aconstant distance between the balls of the ball bearings. In case thatother types of rolling elements bearings are used correspondent rollingelements cages can be used as well but might not be absolutely required.

FIG. 7 illustrates a flowchart of a method invented for camera modulescomprising a movable lens barrel, allowing a maximum lens diameter withminimal outside dimensions. A first step 70 describes the provision of acamera module comprising a movable lens barrel driven by at least onesingle linear actuator. The next step 71 illustrates deploying theactuator in a corner of the camera module. Step 72 describes guiding themovements of the lens barrel driven by said at least one actuator to adesired position by rolling elements bearings. These rolling elementsbearings could be any kind of rolling elements bearings such as e.g.ball bearings, roller bearings, etc. In a preferred embodiment of theinvention two rolling elements bearings have been deployed. Other numberof such bearings could be deployed as well. Step 73 describes applying apre-load force to the rolling elements bearings, wherein this force ispresent in any position of the lens barrel.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention.

What is claimed is:
 1. A camera comprising: an image sensor; a movablelens barrel; at least one linear actuator to move said lens barrel,wherein said actuator is deployed in a corner of the camera module,wherein the actuator generates a pre-load force on rolling elementbearings; wherein at least two rolling element bearings are provided atthe circumferential surface of the barrel, wherein one of said rollingelement bearing is tangentially oriented and the other of said rollingelement bearings is radially oriented, and wherein the pre-load force ofthe actuator comprises a tangential component so that the tangentiallyoriented rolling element bearing is pressed against a correspondingabutting surface.
 2. A camera according to claim 1, comprising a shutterwith an aperture function driven by a linear motor; said motor drivingthe shutter, wherein the motor has an integrated position sensingsystem.
 3. A camera according to claim 1 comprising an integratedcircuit controlling the motor driving the shutter and the actuatorsmoving the lens barrel; and said rolling elements bearings wherein therolling elements of each bearing are moving between the lens barrel anda fixed part of the camera.
 4. A camera according to claim 1 wherein anoffset is implemented between a longitudinal center line of magnets ofan anchor of the actuator and a longitudinal center line of a stator ofthe actuator, wherein the offset generates permanent force in tangentialdirection.
 5. The camera according to claim 1 wherein said rollingelements bearings are ball bearings.
 6. The camera according to claim 1wherein said rolling elements bearings are roller bearings.
 7. Thecamera according to claim 1 wherein protrusions of the lens barrel areused to apply a pre-load force on the rolling elements bearings.
 8. Thecamera according to claim 1 wherein at least one of said linearactuators has an integrated position sensing system